Marine environments sediments

The environmental relevance of anaerobic degradability as a property for surfactants is emphasised by the amount that can accumulate and potentially cause effects in anaerobic environmental compartments. The most important final recipient of surfactants not degraded through various processes is the marine environment (sediments). 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

The widespread use of many metals such as silver, cadmium, copper, mercury, nickel, lead, and zinc has resulted in their accumulation in the environment. Sediments are often the repositories of toxic metals (e.g.. Table 15-2). For example, copper is used as an anti-biofouling agent in marine paints and many harbor sediments contain markedly elevated levels of copper. 

Hill, I.R., Matthiessen, R, and Heimbach, F. (Eds.) (1993). Guidance Document on Sediment Toxicity Tests and Bioassays for Ereshwater and Marine Environments. SETAC Europe Workshop on Sediment Toxicity Assessment. Renesse, the Netherlands, November 8-10, 1993. 

Sulfides and disulfides can be produced by bacterial reactions in the marine environment. 2-Dimeth-ylthiopropionic acid is produced by algae and by the marsh grass Spartina alternifolia, and may then be metabolized in sediment slurries under anoxic conditions to dimethyl sulfide (Kiene and Taylor 1988), and by aerobic bacteria to methyl sulfide (Taylor and Gilchrist 1991). Further details are given in Chapter 11, Part 2. Methyl sulfide can also be produced by biological methylation of sulfide itself (HS ). Carbon radicals are not the initial atmospheric products from organic sulfides and disulfides, and the reactions also provide an example in which the rates of reaction with nitrate... 

Coates JD, J Woodward, J Allen, P Philip, DR Lovley (1997) Anaerobic degradation of polycyclic aromatic hydrocarbons and alkanes in petroleum-contaminated marine harbor sediments. Appl Environ Microbiol 63 3589-3593. 

Where Ao is the activity at the sediment surface, w is the sedimentation rate (cm yr ), D is the mixing rate (cm yr ), is the decay constant for the nuclide of interest (yr ) and z is the depth in the sediment (cm). In some near-shore environments both sedimentation and bioturbation must be considered. But in most open marine environments the sedimentation rate is sufficiently slow that it can be ignored and the equation simplifies to ... 

Lee, R.F., Ryan, C. (1979) Microbial degradation of organochlorine compounds in estuarine waters and sediments. In Proceedings of the Workshop of Microbial Degradation of Pollutants in Marine Environments. EPA-600/9-79-012. Washington, D.C. 

Methylmercury in the marine environment may originate from industrial discharges or be synthesised by natural methylation processes. Fish do not themselves methylate inorganic mercury [62,64], but can accumulate methyl mercury from sea water [63]. Methylmercury has been detected in sea water only from Minamata Bay, Japan, an area with a history of gross mercury pollution from industrial discharge. It has been found in some sediments but at very low concentrations, mainly from areas of known mercury pollution. It represents usually less than 1% of the total mercury in the sediment, and frequently less than 0.1% [65-67]. Microorganisms within the sediments are considered to be responsible for the methylation [65,68], and it has been suggested that methylmercury may be released by the sediments to the sea water, either in... 

Neff, J.M. 1982a. Accumulation and release of polycyclic aromatic hydrocarbons from water, food, and sediment by marine animals. Pages 282-320 in N.L. Richards and B.L. Jackson (eds.). Symposium Carcinogenic Polynuclear Aromatic Hydrocarbons in the Marine Environment. U.S. Environ. Protection Agency Rep. 600/9-82-013. 

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